We report measurements of the beam spin asymmetry in deeply virtual Compton scattering (DVCS) at an electron beam energy of 4.8 GeV using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The DVCS beam spin asymmetry has been measured in a wide range of kinematics, 1.0 < Q2 < 2.8 (GeV/c)2, 0.12 < xB < 0.48, and 0.1 < −t < 0.8 (GeV/c)2, using the reaction epe' p X. The number of H(e, e' γ p) and H(e, e'π0p) events are separated in each (Q2, xB, t) bin by a fit to the line shape of the H(e, e' p)X M2x distribution. The validity of the method was studied in detail using experimental and simulated data. It was shown that with the achieved missing mass squared resolution and the available statistics, the separation of DVCS–Bethe-Heitler and π0 events can reliably be done with less than 5% uncertainty. Also, the Q2 and t dependences of the sin φ moments of the asymmetry are extracted and compared with theoretical calculations.

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Copyright © 2009 American Physical Society. This article first appeared in Physical Review C 80, no. 3 (September 29, 2009): 035206: 1-14. doi:10.1103/PhysRevC.80.035206.

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